Project Abstract. The presence of microorganisms in DNAPL-contaminated porous media systems can enhance or inhibit mass transfer processes depending on the type, quantity, and distribution of biomass. Recent work using high-resolution synchrotron x-ray tomography has demonstrated the ability of researchers to image and quantify pore-scale mass transfer mechanisms in abiotic systems. However, the ability to image and distinguish biomass within the media has not been demonstrated using this high-resolution technique. Because biomass is composed mostly of water, it is difficult to distinguish from pore water. The objective of this project is to systematically test several techniques in an attempt to image biomass in simplified multi-phase porous media systems. Techniques to be tested include colloidal gold-doping of microbial cells, phase-contrast synchrotron X-ray imaging, and the use of agar as a surrogate biofilm to investigate the diffusion of doping agents through microbial systems. The successful imaging technique(s) developed and refined in the course of the research will then be applied to more complex DNAPL systems to study pore-scale mass transfer processes in the presence of microorganisms. Results from this study will also be useful for pore-scale research directed at determining the impact of biomass in other porous media problems (e.g., biofouling).
